1. Field of the Invention
The present invention relates to a reduction in power consumption of a FM radio device.
2. Prior Arts
A reduction in power consumption has been promoted to prolong an operable time in a FM radio device. A conventional measure for reducing power consumption is disclosed in, for example, Japanese Unexamined Patent Application Publication No. 7-212303. This application discloses a power control method for reducing power consumption of an FM radio device.
FIG. 10 is a block diagram showing a conventional FM radio device. In the FM radio device shown in this drawing, radio signal modulated by a baseband signal is received by an antenna 101, passes through a transmit-receive branching filter 102 and frequency converted and demodulated by a receiver 103. The reception electric field intensity of the radio signal is detected by an electric field intensity detecting circuit 104, using a radio signal converted and demodulated by the receiver 103 and the baseband signal, whereby the transmission power information of the station to communicate with is decoded by a transmission power information decoder 105. The transmission power information of the station to communicate with includes information on the radio signal modulated by a baseband signal from the station to communicate with. A transmission power determining circuit 106 obtains a radio wave propagation state between a home station and the station to communicate with by using the reception electric field intensity detected by the electric field intensity detecting circuit 104 and the transmission power information of the station to communicate with which is decoded by the transmission power information decoder 105. A power control circuit 107 is controlled so that the transmission power is one determined by the transmission power determining circuit 106 from the radio wave propagation state. Then, the transmission power information on the home station is coded by a transmission power information encoder 108. The coded transmission power information is added to the baseband signal, passes through a transmitter 109 and the transmit-receive branching filter 102, and then, is transmitted to the station to communicate with by the antenna 101 as a radio wave modulated by the baseband signal.